Spinal position sense is independent of the magnitude of movement.

STUDY
DESIGN: Position sense in the spine was recorded at T1, T7, L1, and S2 in three incremental angular ranges of flexion and on return to upright standing from these movements.
OBJECTIVES: To determine the effect of angular range of movement on position sense. The main purpose was to establish a protocol for whole spine assessment of position sense in healthy and pathologic spines. SUMMARY OF BACKGROUND DATA: Position sense is one dimension of proprioception, classically assessed by the ability to reproduce preselected target positions. This approach was used in the current study to determine whether spinal position sense is affected by the magnitude of movement traversed in repositioning tasks.
METHODS: Spinal position sense was assessed in 20 healthy subjects during repeated flexion movements carried out in one-third, half, and two thirds of the full range of movement in the sagittal and coronal planes. During each movement, the 3-Space Fastrak (Polhemus Inc., Colchester, VT) was used to record angular movement of the spine at four sensor locations (T1, T7, L1, and S2). The absolute difference in the sensor angles between repeated trials was calculated for each flexed position and on return to upright standing from these. These absolute differences were used as a measure of position sense.
RESULTS: Absolute position sense after one-third angular movements was accurate to within 4.30 degrees +/- 2.84 degrees in flexed positions and 2.70 degrees +/- 2.20 degrees in upright postures. Corresponding results for two-thirds movements were 4.75 degrees +/- 2.63 degrees and 3.33 degrees +/- 2.60 degrees, respectively. Range of movement had no significant influence on the accuracy of position sense.
CONCLUSIONS: 1) Healthy individuals are able to reposition their spine accurately under conditions of incremental increases in angular range. 2) Range-related variations in position sense are small and unlikely to be of clinical significance.